The present invention relates, in general, to water purification methods and apparatus, and, in particular, to a new and useful apparatus and method for treating ballast water before it is pumped into the ballast of a ship, barge or other vessel in order to reduce or eliminate the danger of contaminating remote bodies of water with non-indigenous life forms when the ballast water is later discharged into that remote body of water.
Ballast Water Issue
The introduction of invasive marine species into new environments by ship's ballast water has been identified as one of the greatest threats to the world's ocean, coastal and inland waters. To reduce the probability that ballast water contains significant numbers of non-indigenous species, the International Maritime Organization or IMO established a set of voluntary guidelines for the control and management of ships' ballast water to minimize the transfer of harmful aquatic organisms and pathogens. The IMO Assembly first adopted these guidelines in 1997. They replaced earlier, less comprehensive voluntary guidelines adopted in 1993. Management and control measures recommended by the guidelines include: minimizing the uptake of organisms during ballasting, cleaning ballast tanks and removing mud and sediments, avoiding unnecessary discharge of ballast, and undertaking certain ballast water management practices. The management practices include: exchanging ballast water at sea, the non-release or minimal release of ballast water, and discharge to onshore reception and treatment facilities.
An international Convention for the Control and Management of Ships' Ballast Water and Sediments has been adopted by the IMO and announced on Feb. 13, 2004. The Convention will enter into force 12 months after ratification by 30 States.
Beyond the significant efforts being expended by IMO member countries to develop an international legal instrument, many countries and even sub-national jurisdictions have unilaterally developed or are developing national or local legislation. These include Australia, Canada, Chile, Israel, New Zealand, the USA, and various individual states within the USA including all those bordering the Great Lakes, as well as California, Oregon, Washington, Alaska and Hawaii, and various individual ports around the world, such as Buenos Aires in Argentina, Scapa Flow in Scotland, and Vancouver in Canada.
Discharge Criterion and Regulations
The criterion for wastewater treatment and discharge as it applies to vessels is administered on an international, national, state, and even the local levels, with some variation based on route, tonnage, type of vessel, and length of vessel. With respect to ballast water discharges, IMO has established a ballast water exchange standard and a ballast water performance standard. Ballast water exchange (i.e. the replacement of the ballast water while the vessel is at sea in order to reduce the concentration of contaminants) can still be used, for a limited period of time, to meet the performance standard:
Regulation D-1 Ballast Water Exchange Standard—Ships performing ballast water exchange should do so with an efficiency of 95 percent volumetric exchange of ballast water. For ships exchanging ballast water by the pumping-through method, pumping through three times the volume of each ballast water tank shall be considered to meet the standard described. Pumping through less than three times the volume may be accepted provided the ship can demonstrate that at least 95 percent volumetric exchange is met.
Regulation D-2 Ballast Water Performance Standard—Ships conducting ballast water treatment shall discharge less than 10 viable organisms per cubic meter greater than or equal to 50 micrometers in minimum dimension and less than 10 viable organisms per milliliter less than 50 micrometers in minimum dimension and greater than or equal to 10 micrometers in minimum dimension and discharge of the indicator microbes shall not exceed the specified concentrations.
The indicator microbes, as a human health standard, include, but are not limited to: a. Toxicogenic Vibro cholerae (O1 and O139) with less than 1 colony forming unit (cfu) per 100 millimeters or less than 1 cfu per 1 gram (wet weight) zooplankton samples; b. Escherichia coli less than 250 cfu per 100 millimeters; and c. Intestinal enterococci less than 100 cfu per 100 millimeters.
Prior System
U.S. Pat. No. 6,500,345 for an APPARATUS AND METHOD FOR TREATING WATER issued Dec. 31, 2002 is incorporated here by reference and includes a solids separator that is also disclosed in U.S. Pat. No. 6,599,422 issued Jul. 29, 2003 for a SEPARATOR FOR LIQUIDS CONTAINING IMPURITIES which is also incorporated here by reference.
The system disclosed by these patents that are also owned by the assignee of the present application, comprise a centrifugal particulate separator and an UV irradiation system manufactured.